Nitrated diesel fuel and process of making same



May 6, 194i.

c. ELLIS NITRATED DIESEL FUEL AND PROCESS OF MAKING SAME Filed Feb. '7, 1936 4 Sheets--Sheefl 1 C. ELLIS May 6, lg.

NITRATED DIESEL FUEL AND PRCESS OF MAKING SAME Filed Feb. '7, 1936 4 Sheets-Sheet 2 4 Sheets-Sheet 5 C. ELLIS Filed Feb; 7, 193.6

May 6, i943;

I NITRATED DIESEL FUEL AED PRocEss oF MAKING SAME f Patented May 6, 194i Units;

arras. PAT-ENT 4 sales trimaran nrssm. FUEL embraces-ss or :mmc sam:

carleton Memisa, N. s., einem to Standard 011' Development Company, corporation ci Delaware' applicaties sebi-nary 7, i936. serial Nt. 62,759 t (ci. ilasi 1 claim. This invention relates to fuels for Diesel engines and is concerned particularly with petroleum fuels adapted to ignite at relatively lower temperatures under compression.

The widespread use oi engines of the Diesel type has been retarded to some extent by the high compression required to secure adequate ignition speed. This requirement, redected in the inordiengine in the aviation eld. To gain strength without greatly adding to the weight per horse more, this lowering of ignition' temperature is ac-I companied by an increase. in the cetane value of the fuel, that ls, when employed in a Diesel engine the fuel exhibits a higher, or increased, antiknock value.

One procedure whereby I confer on the fuel the quality of lower ignition temperature is by treating such fuel with nitric acid. Nitration may be carried out at room temperature or at higher or lower temperatures. Other nitrating agents which I may employ are mixtures o f concentrated power over the present forms of gasoline-burning 4 aviation engines, resort has been had to costly alloy steels and the like, thereby raising the 'oost of engine construction perV horse power many times that of the gasoline engine. 4

To assist in the reduction in Diesel engineA Weight proposals have been made to add to the fuel a dope of the nitric ester type which would accelerate ignition. For example, the addition of several per cent of ethyl nitrite' or nitrate has been recommended. Efective dopes of this nitro type are costly and although initial yexpense of exi` -gine plant may be reducedJthe expense of operation is increased in considerable measure. Fur- I fuels obtained from petroleum.

The present invention involves the treatment of petroleum and related fuels cheaply to conter thereon the quality of lower ignition temperatures without the necessity of adding ignition temperature depressants, or dopes, made extraneously. It is applicable particularly to non-volatile petroleum fuels of the Diesel type, ithat is, fuels which unlike ordinary gasoline do not spontanecmsly l evaporate when exposed to the atmosphere and which present a very low fire hazard because of their vmuch higher fire and flash points. Eurthersulphuric and nitric acids,l sulphuric acid and sodium nitrate, or the oxides of nitrogen. Thelatter (i. e., oxides of nitrogen) may be prepared by the -action of sulphuric acid on sodium or-po tassium nitrite,- by the action of nitric acid on copper, by the passage of air (i. e., a gas containing both oxygen and nitrogen) through an electric arc, by the catalytic oxidation of ammonia, or by any other convenient method. Preferably a small proportion of air, or ,other oxygen-containing gas, is mixed with the oxides f nitrogen before passing into the oil. With some types of Diesel fuel liquid oxides of nitrogen, instead of the gaseous oxides, may be employed as the nitrating agents. V

Although concentrated nitric acid or mixtures of concentrated nitric and sulphuric acids or of concentrated sulphuric acid and sodium nitrate may be employed, lpreferably I dilute such nltrating agents with water until the concentration of the reactive agent, ory agents, is that represented approximately by the sludge-minimum point, i. e., the concentration of the nitrating agent at which substantially no sludgeIA or only the minimum quantity is formed during the nitration step and simultaneously nitration of the oil proceeds to a degree sumcient to yield a fuel of lower ignition temperature (as determined by the hot plate method). It is also desirable that the concentration of the nitrating agent be such that substantially no oxidation ofthe hydrocarbon constituent of the iu'el to acidic bodies occurs.

Instead of using commercial sulphuric acid I may employ the acid recovered from the sludge produced in the sulphuric acid rening of petroleum, or other related hydrocarbon, distillates. Recovery of acid from such sludge can be accomplished by diluting the latter, for example, with one or two volumes of water and removing thev insoluble portion which separates on dilution. In some instances, e. g.. when the proportion of water-insoluble material is smallor when such material exerts no 'deleterious elect on the fuel being treated, dilution of the 4sludge with water,

prior to use, can be omitted.

It isdesirable in the nitrating operation that vigorous oxidation, or other objectionable reaction, resulting in the formation of` sludge be avoided in so far as possible. As previously mentioned, the concentration of the nitrating mixture preferably should be at the sludge-minimum point. For this reason, the proportion of nitrating agent and the temperature of nitration will vary with different fuels, although generally the more dilute the acid employed the higher the temperature at which nitration is effected. The

exact strength of the nitrating agent and the" temperature required for any individual fuel will therefore vary withthe degree of unsaturation and other chemical characteristics of'the oil. With some oils intended for Diesel fuel it may be necessary to treat firstl with a small proportion of concentrated -surphuric acid, and Aafter-- 'wards subject the treated oil to the action of .the nitrating mixture. 'In the preferred method, however, I omit this preliminary treatment with sulphuric acid. Furthermore, since nitro compounds, as a rule, exhibit a specific gravity greater than the 4corresponding 'hydrocarbons and in the preferred method of operation little or no sludge is formed, the increase in specific gravity ofthe treated. fuel may be taken as a qualitative indication of the degree of nitration attained.

, 'Mild nitration of Diesel fuel often results in very little change occurring in the specific gravity or ash and fire points of the oil,bu t with increasing nitration both the fire and iiash points as well as the specific gravity of the fuel become higher. At the same time the temperature at which ignition of the fuel takes place is greatly decreased. This lowering. of ignition temperature accompanied by a decrease in fire hazard (i. e., increase in flash and fire points) brought about by nitration of the fuelv is a surprising yassauts formed by the expected interaction of sulphuric acid and sodium nitrate in the first case.

One procedure for treating Diesel fuels consistsvin mixing the oil and nitric acid (or nitratingmixtureh the temperature being mainvtained, for example, by heating or cooling coils, as the case may be, and agitating the mixture untilthe desired degree of nitration-is attained. The mixture then is allowed tov settle and the acid and oil layers separated. l'Ihe oil is washed 1- with water orother washingand/or neutralizing medium to remove free acid and, if necsary, is

filtered through an inert material, e. g`., tine `sand, to eliminate small dispersed particles of sludge. Modifications of this procedure are the addition of the nitrating agent in two or more portions to the oil or of the 'oil in two or more portions to the nitrating agent. Other modifiy cations can be secured by varyingv the temperature. Thus, a portion of lthe nitrating agent can be added and the temperature of treating kept at, say, 0 C. After the more reactive constituand unusual combination of properties which I l regard as being particularly advantageous in the use of heavy non-volatile fuels of the Diesel type. Another advantage of nitration is the marked improvement in odor of many fuels, more ,especially those fuels containing mercaptans and other compounds possessing disagreeable odors.

The accompanying 'drawings or graphs indicate an increase of specific gravity with increase in degree of nitration; also certain changes in flash and re points and ignition temperatures as nitration progresses and the effect of addition of extraneous nitro compounds on flash and fire points. In the drawings'Fig. 1 serves to illustrate the increase in dash and fire points of a Diesel fuel with increasing degree of nitration as indicated by the specific gravity of the product. Fig. 2 shows the decrease in flash and fire points of untreated Diesel fuel due to the addition of nitroethane, and the decrease in these same properties of'a nitrated fuel on the addition of nitrate. Fig. 3'represents the increase in degree of nitration, as indicated by the specific gravity of the oil, ywhen various concentrations of nitric acid are employed in the nitration of Diesel fuel. Fig. 4 indicates the decrease in ignition temperature ofthe fuel (as determined by the hot plate method) with increase in specific gravity due to nitration. References to these drawings will be made in various places throughout the specification.

In some instances it may be advantageous to employ catalysts in the nitrating step. One ex- 75 ents of the oil have become nitrated, more of the agent is 'added and the temperature increased to, say, 60 C. Or, partial nitration may be effected by employing dilute nitric acid, e. g., sp. gr. 1.05, followed by treatment with more concentrated acid, e. g., sp. gr. 1.10. Many other modified .procedures involving the temperature. of reaction, strength of nitric acid or other n itrating agent, and the stepwise addition of nitratingl agent or of oil, are possible as will be evident.

y Although the pour points of fuels of the Diesel type are"`generally very low, e. g., about 40 C; (-40" FJ, nevertheless nitration of the fuel is often accompanied by an increase in the pour point of the oil. In the preferred method, ni-

tration of the fuel results in only a small increase in temperature at which the oil will pour, thereby yielding a fuel which is readily fiowable even 'at relatively low temperatures.' In those cases where the pour point of the nitrated oil has been increased to an inordinate degree, the product may be treated to remove the objectionable thickening bodies to the extent necessary or required'.

In some instances nitrated Diesel fuels or blends of nitrated and non-nitrated fuels will deposit a very small proportion of sediment, or sludge, during storage. The presence of insoluble material, even in minute quantity, is highly -undesirable in Diesel fuels as the accumulation: 'of such deposits in the fuel jets quickly results in their becoming more or less closed, thus resulting in reduction of the fuel supply tothe engine.

In cases when the fuel is used at not too great v an interval after beingprepared, incorporation of an oxidation inhibitor, of which a-naphthol is an example, may retard sludge-formation suff lciently to permit the fuel being employed without any ill be necessary to age the fuel, i. e., keep it stored, until deposition is substantially complete. This aging may be done at atmos- A effects on the engine. In still other cases it may fore, highly undesirable.y stances from petroleum fractions may be accomaasd'ssa p herie temperature, or at somewhat elevated temperatures, e. g., 90 C. rEither the nitrated fuel maybe aged, the resulting sludge removed by'iiltration or other'means, and the aged fuel blended'with a non-nitrated fuel, or the blended fuel may be aged and any precipitated material gine. vC )nel procedure whereby such action may be inhibited is the addition of a small proporf tionl of an antacid, e. g., aniline, triethanolamine or gaseous ammonia. Another. method of reduc..

. ing'corrosion consists in subjecting the nitrated fuelto a mild reduction by hydrogen or other reducing agents. Furthermore, corrosion of metals by nitrated Diesel fuel can be minimized byavoiding exposure of the -fuel to moisture or to sunlight.

It has beennoted that some petroleum distillates, intended for use as Diesel fuels, contain a-small proportion of bodies presumably of the -phenolic type. Phenolic compounds, as a rule,

aregeasily nitrated yielding products which are strongly acidic in character and which readily coi-rode metals. The presence of phenolic bodies in Diesel fuels which are to be nitrated is, there- Removaljof such subplished, for example, by. washing the distillate with an aqueous alkaline solution or by treatment with solid alkali, e. g., sodium hydroxide. Such treatment prior to nitration not only yields a nitrated Diesel fuel of greatly reduced conceive action, but also decreases the proportion of sludge formed during the nitrating operation.

As stated in Serial No. 670,753, nitrated fuels may be used alone or, ifdesired, may be blended with non-nitrated fuels such as normal Diesel oils or hydrogenated-oils including those which have been made by hydroforming (hydrogenolysis) and milder treatments of the hydroning type. For example, blends in some cases maybe constituted of equal volumes of a nitrated and a non-nitratedoil. In other cases one-fourth part or less of the nitrated or non-nitrated oil may be present, and the remaining three-fourthsA part or more being composed of the other constituent, or other proportions used.

latter are exposed to wide variations in atmospheric pressure and temperature.

In some cases I may add to the non-nitrated l Diesel fuel an auxiliary primer made by nitrating non-volatile petroleum oils or fractions which possess boiling ranges of approximately the same orhigher than vDiesel fuels. Examples of such oils are 'the white oils obtained by the drastic treatment of gas oil, or higher-'boiling distillates, with sulphuric acid. In other cases I may employ, as the material to be nitrated, such semisolid or lsolid petroleum fractions as petrolatum,

v aseline, sweater-oil, or paraffin wax. These liquid, semi-solid, or solid petroleum fractions can be nitrated by any of the vpreviously-mentioned procedures and the resulting product, consisting for the most part of nitrated and nonnitrated petroleum hydrocarbons. added to the Diesel fuel in ignition-temperature-lowering' proportions.

Addition of nitrated semi-solid or solid petroleum fractions, because of the presence of non- -nitrated hydrocarbons, may result in` some instances in an undesirableincrease in the pour point of the Diesel fuel. Thus Diesel fuel containing dissolved nitrated paraiiin wax, for example, when subjected to a lowering of temperature, e. g., when exposed to cold weather, may become-sumciently viscous and cease to ow readily or, if the temperature loweringis suiilciently great, may even become solid and non-fiowable. Such physical changes in the oil would result in a partial or complete plugging of the fuel lines from the feed tank to engine or to the fuel jets, thereby resulting in faulty performance or stalling of the engine. To overcome this diilicuity I may, e.. g., extract the nitrated semi-sona or solid petroleum fractions with a selective solalcohols, and ethylene dichloride. Extraction I may also lower the temperature of ignition of normal Diesel fuel by incorporating substan.. tially at the time of use a desired proportion of nitrated fuel or of substances capable of causing such lowering. One way of accomplishing this `regulation and adjustment is the use of two fuel tanks, one of which .holdsl the nitrated fuel (acti- .listing liquid) or other ignition-temperature delfeSS'ant and the other holds the Diesel oil norrequired. Streams of liquids from both tanks pass" through a mixing chamber before introduction into the engine. By regulating the flow of the activating liquid a greater or lesserv lowering of ,ignition temperature may be secured.

`other convenient operation may be carried out at atmospheric temperature or at lower temperatures, the latter being par-A ticularly advantageous as the solubility of the non-nitrated petroleum hydrocarbons is greatly reduced thereby. A fterextraction is complete,

undissolved non-nitrated petroleum hydrocarbons are separated from the 'solution of nitrated petroleum hydrocarbons. The solution may then be subjectedto evaporation,

whereby the solvent is removed from the nitrated hydrocarbons. In

this manner I obtain a concentrate of nitrated petroleum hydrocarbon ignition temperature d epressants which may be added to Diesel fuels in proportions sumcient to 4secure the desired ignition temperature lowering. The non-nitrated portion can again be subjected to nitration and solvent extraction whereby an additional concentrate of nitrated tained. l

Insome instances it may be desirable to extract nitrated Diesel 'fuel-with a selective solvent thereby obtaining a concentrate of lignition'v temperature depressants. An example of a se,- lective solvent which I have found suitable for this purpose is aniline as it is soluble only to a limited degree in the fuel at atmospheric, or a lower, temperature. After extraction of the nitrated oil, the aniline solution of ignition temperature depressants is treated, eg., with an aqueous solution of a mineral acid whereby the aniline is dissolved leaving an insoluble concendistillation, or any.

petroleum hydrocarbons is ob-l trate of ignition temperature depressants. The extracted fuel may be washed with dilute acid',

to remove any dissolved aniline, and again 11itrated and extracted to yield an additional concentrate of v ignition temperature depressants.

I Extraneous nitrated 'ignition temperature depressants which are particularly suitable vfor my purpose are those obtained by the nitration of polymerized isobutylene, preferably the trimeric or higher polymeric isobutylenes,or mixtures of these polymeric hydrocarbons. Such polymers, or mixtures thereof, Vexhibit boiling ranges coniparable to those of petroleum oils normally suitable for Diesel engine operation. Isobutylene f (which boils at 6 C.) occurs to the extent of about 4 per cent by weight, or more, in the gases obtained by 'cracking petroleum distillates, e.g.,

and threefourths part by volume of suitable' hytrate.

. move free acids. y l

AExample 2.-'-The following series of results gas oil or heavier fractions.- It; may be separated from associated gaseous hydrocarbons by liquefaction of the mixture followed by fractional distillation, or by any other convenient method.

kPolymerization of isobutylene to the dimericf, tri'- Amerio, or higher polymers is accomplished with the aid Iof catalysts such as boron triiiuoride,

' dilute sulphuric acid (e. g. 65-70 per cent acid) or Unchanged isobutylene and.

aluminum chloride. l diisobutylene can be separated from the polymerlf ization product by distillation leaving a residue of ltriisobutylene and higher polymers. Treat-l ment of these residual polmyers with nitric acid,

' sodium nitrate and sulphuric acid sludge; oxides of nitrogen, or other nitrating agents furnishes nitrated hydrocarbons which may be ladded to I nitrated or non-nitrated Diesel fuels as ignition temperature depressants. Alternatively, the iso-- butylene polymers can be blended with untreated Diesel fuel and the blended fuel subjected to the action of nitrating agents.

drogenated oil,.to which is added 1 perfcent by volume of 2methyl2-, nitropropane1,3-dini- The following examples will illustrate my invention.

Eample 1.-0ne hundred-parts of Diesel fuel are agitated with 1 volume of concentrated sullphuric acid.. The mixture is allowed to settle and the acid layer withdrawn. 'One hundred volumes yof the acid-treated fuel are nitrated'l by agitating for 30 minutes with 2.5 volumes of a nitrating mixture-consisting of equal volumes of concentrated sulphuric and nitric' acids. The

acid layer is withdrawn and the nitrated fuel .washed witlrwater orfneutralizing agents to reshows the effect on sludge formation, specific gravity, and behavior of fuel'when dropped on a hot plate, when low-grade Diesel fuel is treated with nitric acid of different concentrations and at different temperatures. -The time of nitration treatment varied from 4 to 5 hours.

' Vol. 4Vol. Bp Per Bp., Hot- Run No. of oi `o Temp. cont of prodlato fuel acid acid sludge uct avior 0.927 Didv no nite. ,1.09 100 1-2 0.932 o. 1.09 .100 l2 0.938 llfgnites.

1.09 70 1- 0.942 Do. 1.14 100 25 0.950 Do.

'The above data indicate that nitration of. the fuelis accompanied by an increase in specific gravity. With this particular fuel, when the specific gravity reached a'value of 0.938, hot- Although I prefer to exclude addition of costly onion cmcmNozHcHo cns- Nol v mon CHzOH CHINO: cm-c-Nozmroi cin--l Noi-211,0

11,011 Ilmo Analogous nitrodihydroxy alcohols, which in turn may be converted to the corresponding di:-

nitrates, are obtained by the substitution of acetaldehyde for formaldehyde. Although I may add such nitrated ignition temperaturedepressants, e.g., 2-methyl-2-nitrOpropane-LS-dinitrate, made from extraneous sources to normal Diesel fuels., preferably such ignition temperature "depressants, or primers, are incorporated as auxiliary primers withv nitrated Diesel fuels or with blended fuelsA one constituent of which is nitrated Diesel fuel.' An example of the latter is a blended fuel, comprising onefourth part by volume of nitrated Diesel fuel plate ignition readily took place. Furthermore, by 4regulating thel quantity of acid employed, its

'ncentxation, and the temperature.' nitration Y can be eifected with formation of veryy little sludge.

Emmple 3.-The approximate minimum ignition points (as determined by dropping the fuel on Aa hot plate) of theproducts obtained in Exiample 2 are given in the following table:

s Aigprox. l

m imum. Product ignition temperature c. Untreeted hiel 0.927 550 Runl 0.932 550 Run 0.938 500 Run 0.942 500 Runi 0.950 430 Referring to Fig. 4, in which is plotted ignition temperature `against specific gravity, it is noted that as the specific gravity increases. due to nitration of the fuel, the ignition temperature of the oil is substantially decreased.

Example 4.-1The results tabulated below were obtained witholombian Diesel fuel.

Vol.4 Vol. 8p. Sp.gr. RunNo. of of .of Tem Time mnt oirodfusi wie l5.1m p am gcc Unti'eated 0. Hour:y t fuel 0. uz 25 1.09 7o s 1 0.869 50 1.00 50 7 i 0.854 so 1.00 70 4 1 0.855 so 1.00 70 12 1 0.880

Only the product. obtained in Run l,

a specific gravity of 0.880 ignited readily when dropped onto a hot plate.

Example 5.-'Ihe approximate ignition points and the ash and fire points of the products ob- Example 9.-Colombian Diesel fuel was heated to l'10" C. and," while kept at this temperature, a stream of dry oxides of nitrogen, diluted with air, was passed through the liquid for 5 hours. Very little sludge wasformed and the specific gravity of the oil increased from 0.847 to 0.862. In this instance the oxides of nitrogen were obtained by the action of nitric acid (l volume of concen- The above data indicate that both the flash point and lire point increase with` the degree of nitration. The increase in flash and re points with increase in specific gravity of the fuel are represented graphically in Fig. 1.

Example 6.--Diesel fuel from a Pennsylvania crude petroleum was treated'with nitric acid at atmospheric temperature for 8 hours. In each `instance 250 volumes of oil and 50 volumes of nitrating agent were employed. The speciiic gravity of the nitrating agent varied, in the different runs, from 1.09 to 1.42. The results obtained are given in the following table.

Speclc Specific f gravity Color ol f gravity Percent Hot-plate nu of product of sludge behavior acid product Untreated Golosinas---" 0. 825 Did not ignite mel. at 550 C. 9 1.09 dn .825 Do. 10 1. 15 Lightyellow. .825 Do. 1l 1.20 dn .828 D0. l2 1.30 Yellow .827 1 Do. 13 1. 37 Orange-yel- 835 l I g n it es e t low. 4009 14 1.42 Orange .839 4 Ignites at The relation between the specific 'gravity of the nitrated fuel and the specic mvity of the acid employed are shown in Fig. 8. Example 7.-'-To 250 volumes of Coloxx'ibiau.-

Diesel fuel were added50 volumes oi an aqueous solution containing 2.594 moles of mdium nitrate and 2.79 moles of sulphuric acid per liter of solu- 1 tion. (Assuming all the sodium nitrato to be converted into nitric acid by the sulphuric acid,

the concentration of nitric acid is very close to that of a solution of nitric acid of specic gram trated acid and l volume of water) on copper.

Eample.10.-Nitration is effected by conducting a stream of oxides of nitrogen, mixed with air, into Diesel fuel kept at atmospheric temperature. In this case, the oxides of nitrogen were generated for the purpose by the action of sulphuric acid on sodium nitrite.

Example 11.-As shown in Example 5, the llas .and re points of an untreated Diesel fuel are 161 F. and 180 F., respectively. When 5 per cent by volume of nitroethane (boiling at 238- 239 F.) is added to this fuel the ilash land fire points of the blended fuel were found to' be 97 F. and 111 F., respectively.

Example 12.-Nitrated Colombian Diesel fuels containing an auxiliary primer were prepared by adding 5 per cent by volume of nitroethane or of 2-methyl-2-nitropropane-1,3-dinitrate (as made according to Example 20) to the fuel made according to Run 'l in Example 4. The flash and re points of these fuels were found to be as The above data, and also that given in the preceding example, were used to plot the curves shown in Fig. 2.

Example 13.-The lowering of there and flash points of a Pennsylvania Diesel fuel due to the addition of 5 per cent by volume of ethyl nitrate (boiling 188-190" F.) is given in the following table.

` 1 h Flr Fuel goaiit poiiftf w. a Penn. Diesel 274 299 Penn. Diesel+5% ethyl nitrate 115 296 Example 14.-The pour points of some of the fuels described in Example 2 were found to be as follows: y

P Pour roduct Sp. gr. point at 70 C. with nitric acid of specific gravity 1.09. 1

Example 8.-Acid sludge obtained in the sulphuric acid reiining of water white was diluted with an equal volume of water. The' aqueous manner )in the nitration of Colombian Diesel fuel. Sodium nitrate was added to the aqueous layer in the proportion of 2.594 mol per liter.' Efty volumes of the resulting solution wereagitated with 250 volumes of Colombian Diesel fuel at 70 C. for` 8 hours. The oil product, after washing, drying and filtering through sand, had a specific gravity 0.864 as compared lmtreated fuel.

layer, sp. gr. 1.24, was employed in the. following with 0.347 for the Example 15.-The pour points yof. the fuels described' in Example 4 are tabulated below:

Product Sp.

dropped on a hot-plate, did not explode Example 16.-One hundred parts of hard white paramn wax were treated at 100 C. for 25 hours with concentrated nitric acid and aluminum nitrate. Forty-three parts of acid were initially added, two equal 'portions (of v43 parts each) of acid were added during the course of nitrat'ion, one at the end of 7 hours and one at the end of 14.5 hours, and a third portion of 21.5 parts of acid was added at the end of 22.5 hours. One hundred and twenty-two parts of valuminum nitrate, A1(NO3)3-9H2O, 'were employed as the catalyst. The product, after removal of the acid layer and washing with water, was a yellowcolored, soft," low-melting solid. This product may be added to Diesel fuel, for example, in

proportions of 2%, 3%,"or 5% by weight, to

decrease the ignition temperature of the fuel.

Example 17.-A portion of the product from Example 16 was extracted at room temperature with acetone, using 41 parts of nitrated paraffin wax' and 40 parts of acetone. In this instance extraction yielded 29 parts of light yellow-colored acetone-soluble material, and about 12 parts of pared in Example20 may be employed as an auxiliary ignition temperature depressant when added to nitrated Diesel fuel in the proportion of 1 part by volume to 16 parts by volume of the fuel.

Example 23.--A portion of the nitrated fuel, as prepared in Example 9, was stored in a closed container for 12 days. At the end of this period a small quantity of black deposit had formed. This .24 Vhours at 45-50" C.failed to produce any addi-- tional dark colored deposit.

Example 24.-Four volumes of polymerized 'isobutylene (consisting prineipauy or `the trimeiic almostwhite acetone-insoluble material. Addioration from the yellow alcoholic solutiono'f nitrated bodies. The extract so obtained,

amounting to 6.4' parts by weight, was a deepr yellow colored, viscous oil which ignited more readily on a hot plate than the residue from the extraction step. l

Example 19.-.Two volumes of nitrated Diesel fuel (Run s, Example 4) were agitated with 1 volume of aniline. After allowing the mixture to separate, the oil and aniline layers were separated. The aniline layer was washed with dilute hydrochloric acid and then with water (to remove aniline and acid, respectively) andthe product obtained was a dark red, viscous, oily material After separation of the nitrated oil layer it was which ignited spontaneously on a hot plate. The

extracted Diesel fuel was washed also with dilute acid`and water (to' remove aniline and acid, respectively) and when tested on a hot plate failed to ignite, although the priginalnitrated fuel ignited easily under the same conditions.

Example 20.--Formalin (equivalent to 2 moles of formaldehyde) containing a trace of dissolved potassium hydroxide was added to nitroethane (1 mole). The resulting clear solution was heated for a short time at -60 C., to complete reaction between the aldehyde and nitroethane, and then evaporated to dryness. The crude, solid nitro-diol(2-methyl-2-nitro-1,3-propanediol) was nitrated at 0- C. with a nitrating mixture consisting'of 3 parts of ruining nitric acid and 5 vparts of concentrated sulphuric acid. A heavy,

yellow oiljzwas formed which was washed with vwater `(to'remove any free acid) and dried. This oil, although it ignited spontaneously when when struck or when fired in a rifle cap. 'f

l AExample 21.-The oily nitrated product as pre- ,pared in Example 20 may be employed as an ignition temperature depressant for Diesel fuel when added in ratio of 1 part by volume to 36 parts by `oieienninea'by engine tests) of and higher polymers) were treated, at`-C., for 8 hours Iwith 1 volume of nitric acid -(specific gravity 1.20). No sludge was formed during nitration. This treatment increased the specific gravity of the fuel from 0.761 to 0.864 and lowered its ignition temperature from 660 F. to

395,211'. Addition of 1 percent by volume of the nitrated product to Colombianand Pennsylvania` Diesel fuelslowered their ignition temperatures by 8 I". and 12 F., respectlvely.

Example 25.-Pennsylvania Diesel fuel was agitated for 8 hours at room temperature with 20l per cent its volume oi' nitric acid (specific gravity 1.42). About 2,per cent of sludge was formed.

washed with water, and then treated with solid magnesium carbonate to remove acidicV bodies. The nitrated product possessed a cetane number of 84 (determined by engine test) as compared with-62 cetane number for the untreated fuel.

Example 26,.-To 5 volumes of Colombian Diesel oil was added 1 volumeof nitric acid (speciiic gravity 1.09) and the mixture was stirred for 11 hours at 70 C. A small amount of sludge (1%) was formed during 'nitration' and the specific gravity ofthe voil changed from 0.850 to 0.870. The' nitrated product possessed a cetane number 67 as compared to 44 for the untrea oil.

y .Example 2?.-Twenty volumes,- of` Colombian Diesel oil v(speciiic gravity 0.850) we re treated at 70C. .with 1 volume of nitrating mixture consisting of acid-sludge and sodium nitrate (see Example 8) -for 8 hours. The specific gravity of the product was 0.860. The nitrated oil possessed. a cetane number of 54 'as compared to 44 for the untreated fuel.

Example 28.-Nltrogen determinations were made on the nitrated Colombian fuels prepared in Examples 26 and 27. The increases'in specificl gravity, percentage of nitrogen,` and cetane num? bers are tabulated below:

Fuel 'Specific Catane Pant gravity number nitrogen Example 29g-One volume of the product from .Example 26, possessing a cetanenumber of 67, was blended with 1 volume of untreated Colombian oil (cetane number. of 44) to give a fuel having a cetane 'number of 61. Also 1 volume of the product from Example 26 .was blended with 3 volumes of untreated Colombian oil to yield a fuel possessing a cetane number o f 48.5.

gravity 1.42).

Example .la-Twenty volumes of Pennsylvania Diesel fuel and 1 volume of nitric acid (specific gravity 1.35) were stirred at atmospheric temperature for 12 hours. and the nal product was orange colored. In this instance the specific gravity of the untreated fuel was 0.825 and that of the nitrated fuel was 0.827. The dash and re points voi.' the untreated oil were found to be 274 F. and 299 F., respectively. For the nitrated oil the fire and flash points were 277 F. and 299 F., respectively. The cetane number of the fuel was increased from 63 to 80 by the treatment 'with nitric acid. The nitrogen content of the nitrated fuel was 0.32 per cent.

Example 31.-Ten volumes of Pennsylvania.

Diesel fuel were agitated. at room temperature, for 12 hours with 1 volume of nitric acid (specific The nitrated fuel, orange in color and possessing a speciflcgravity of 0.842, was blended with varying amounts of untreated Pennsylvania Diesel fuel to give three blended fuels: (A) containing approximately 2 volumes of nitrated fuel and 1 volume of untreated fuel, (B) consisting of approximately l volume of nitrated No sludge was formed tity of sludgevobtained was about 0.25 per cent,

as compared with l per cent for Run 7, Example 4.

From the foregoing it will be seen that my invention contemplates the` process of treating petroleum oil, of the usual specific gravity and of recognized boiling range of fuels employed infl Y Diesel engines, with nitratng agents including nitric acid, nitric-sulphuric acid mixtures, oxides,

of nitrogen, and the like. In the preferred method, treatment of the fuel is accompanied by sludge minimum-point, i. e., nitrating agents yielding 4the minimum quantity of sludge when 5 employed in the treatment of Diesel fuels thereby fuel and 1 volume of untreated fuel, and (C) made by adding 1 volume of blend (B) to -1 volume of untreated fuel. The cetane numbersof Athe various blends were found to be as follows:

(A) 86; (B) 82.5; (C) 72. The cetane number ofl the untreated Pennsylvania oil was 63.

Example 32.-Several mixed fuels were prepared by blending Blend A from Example 3l with Example S32-The increase in cetane number with increase in nitrogen content for the blended fuels described in Example 31 is given below:

` Cetane 'Percent Fuel number nitrogen 63 0. 001 72 0S 82. 5 17 Blend A 86 26 Calculated.

Example 34.-.A Colombian Diesel fuel was repeatedly washed with portions of concentrated aqueous sodium hydroxide solution until the oil was substantially free of phenolic bodies. The presence of such bodies was tested for in the'following manner: A small portion of the oil was withdrawn and shaken witha few cubic centimeters of aqueous sodium hydroxide solution.- To the alkaline solution was added a few cubic centimeters of toluidine diazoniumrchloride solution,

prepared from toluidine, hydrochloric acid, and

sodium nitrite. The development of a red color was taken as an indication of the presence of phenolic compounds. y if Example 35.-The substantially phenol-free lDiesel fuel, prepared in Example `r34, was nitrated 'according to Run "I, Example 4, except that the heating time was extended to 5 hours. The duan- `producing fuels vof lower ignition temperatures.

It also involves the treatment o'f petroleum fractions yheavier than Diesel fuels with such` nitrating agents, separation of the 'nitro products formed thereby fromthe non-nitrated petroleum hydrocarbons, and adding these nitro products to Diesel fuels in proportions sufficient to effect igniy tion temperature lowering., f

In this specification-the term ignition tem-- spontaneous ignition or inflammation (not merely evaporation) of the Diesel fuel when the latter is dropped on it. f

It will be noted that rthe methods of nitration Aherein described are applicable to Diesel fuels obtained from several sources. Such methods may, be applied also to many other types of Diesel fuels including hydrogenated fuels and the like.

' The optimum conditions of nitratiom e. g.,-th`e concentration of the nitrating agent or agents, the'proportions used, temperatures employed, or duration of treatment, will depend upon the chemical and physical. characteristics of the fuel at hand. -Y l Y It is important to recognize that the fuel bf the present invention should not be confused-With gasoline fuels asycusdtomarily used in automobile engines of the, regulation spark ignition fourY cycle type. The new fuel is largely, or wholly heavier @han `gasoline and lis not readily ignited like gasoline by approach offiame. ADiesel fuels arexsubstantially non-volatile hydrocarbon oils generally boiling within ythe range of about 300 to, 600 F., and usually exhibiting a. specificf i gravityof about 0.80 to 0.90 or higher. On the properties as to thrust upon the new fuel the other hand, ordinary' gasoline; boils from about to 400 F., with a specific gravity of approximately 0.70 to 0.74. Again, the dash point of Diesel fuel ordinarily should not be lowerfthan F., or thereabout. On the other'hand 'theflash point of commercial `gasoline is quite low, being around 15, F. and even lower. Furtherymore it is notan object so to lower the ignition fire hazard commonly associated withgasollne, but rather to lowerl in moderate degree the ternperature of ignition under Diesel compression conditions and simultaneously' increase "the gine and for which its usein airplane propulsion is advocated.`

My invention also. provides a step in the ope eration of Diesel engines exposed to rapid varia- Vtion in atmospheric pressure which consists in altering, in accordance with the pressure fluctuation, the proportion Iof catalyst (ignition temilciently to -allow its being employed in Diesel engines.

What I claim is: A method of improving the ignition quali-ty of 5 a Diesel fuel for more eillcient combustion in a compression-ignition engine, which comprises mixing a petroleum distillate Diesel oil having a higher boiling range than gasoline and a cetane number higher than about 44"with dilute nitric 10 acid of specific gravity from about 1.09 to about and sulphuric acids on paraillnic or cyclic hydrocarbons, but also such nitrogen containing compounds as nitrosites and nitrosates. ".lhe former type (nitrositesl are the compounds formed by the interaction of nitrogen trioxide and oleilns, while the latter (nitrosates) are the results of the reactionv between olefins and nitrogen tetroxide. 'I'he olens may be either acyclic or cyclic.

1.37 in proportions ranging from about equal volumes of the Diesel oil 'and acid to 5 volumes of the Diesel oil to l volume of the acid, maintaining the resulting mixture t a. temperature l5 below 100 C. for alperiod adequate to form oil- In some instances nitric acid reacts directly with r certain types of unsaturated hydrocarbons forming addition productsvof the nitro typ. All 'such compounds, containing' these various nitrogenserve to depress its ignition temperature sufsoluble ni-trated derivatives from some of lthe oil 'components without substantial oxidation of the oil to acidic bodies and to form .less than about 1% of sludge impurities, said nitration'being 20 limited to materially increase the nitrogen'content of the oil by about'0.06 to 0.42% through the formation of said nitrated derivatives, and thereafter recovering the treated oil containing said nitrated derivatives in solution by separation `oxygen groupings, when present in the fuel may 25 of any excess spent nitrating agent therefrom CARLETON ELLIS. 

